The broad objective of the proposed research program is to use a cognitive-neuropsychological approach to investigate the role of the frontal lobes in human memory. In this approach, behavioral analyses of neurological patients are used to provide an understanding about the neural systems underlying cognitive function. In the proposed studies, patients with frontal lobe lesions will be evaluated on a series of memory and cognitive measures to evaluate a theoretical view of frontal lobe function. The importance of the frontal lobes to memory function has been a rather controversial issue. Some have suggested that memory impairment in patients with frontal lobe lesions is secondary to disorders of other cognitive processes, such as attention and planning. Others have emphasized the direct role of the frontal lobes on memory tests such as delayed response, short-term memory, and memory for temporal order. In the proposed investigation, three domains of cognitive function will be assessed in patients with frontal lobe lesions: 1) selective attention to stimulus features, 2) interference effects in memory, and 3) memory for spatial-temporal context. It is suggested that impairment of a gating or filtering mechanism mediates many of the deficits associated with frontal lobe lesions. That is, it is hypothesized that cognitive and memory disorders result from a failure to gate inappropriate stimulus features, memories, or responses. Central research questions about memory and the frontal lobes include the following: What is the relationship between memory and other cognitive disorders observed in patients with frontal lobe lesions? What is the relationship between memory and other cognitive disorders observed in patients with frontal lobe lesions? At what stages of memory function do the frontal lobes appear to make significant contributions - stimulus encoding, access of semantic memory, memory storage, or memory retrieval? Are disorders of temporal order memory associated with disorders of gating or inhibitory control? An attempt is made to integrate information from a variety of research domains. For example, both memory and other (non-memory) cognitive abilities will be assessed. Moreover, quantitative analyses of neuroimaging data (e.g. magnetic resonance, computed tomography) will be used to determine if specific areas within the frontal lobes mediate cognitive or memory function. Finally, all study patients will have been tested in electrophysiological studies of attention, as a result of participation in an independent research program. Thus, the proposed project has the opportunity to offer an analysis of memory and cognitive disorders associated with frontal lobe lesions and to integrate behavioral findings with neuroimaging and physiological findings.